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  3. Training Module #2: The Analysis Workflow

Training Module #2: Analysis Workflow (Click-Along)

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Aerospace stress analysis methods simultaneously executed to thousands of load cases. Immediate interactive feedback to the engineer on the FEM: critical failure modes, load cases, and margins of safety. Read an overview of the intentions of the Analysis Workflow here.

Summary

You are the engineer in charge of assessing the margins of safety of the existing Composite Crew Module (CCM) design – in preparation for certification/part release

Model Specs

Solver: NASTRAN

Element Count: 203,321

Load Cases: 11

Desired Safety Factor: 1.4

Analysis Temperature: 72F

Using HyperX:

  • Assess the as-modeled design for pre-defined company margin policy.

  • Generate element-based margin of safety plots for specific portions of the vehicle.

  • Interrogate and mitigate persisting negative margins.

image1.png

Part 1: FEM Import and Setup

Open Database + Project

Path: C:\HyperX\Training\[Version#]\

Database: Training Module #2 - Analysis Workflow_[Version#]

Project: Analysis Workflow - CCM

00_OpenDB_CCM.png

Note

If prompted in Project Options, select Analysis Workflow – CCM and select ‘Open Project’

Import FEM

  1. Click the "FEM Import" button on the Model Tab of the Ribbon.

  2. Click "Add." Then, use the browser to navigate to: C:\HyperX\Models\Astronaut-Composite Crew Module folder and select CrewModule.dat

  3. Change FEM Mass units to Slinches.

  4. Click ‘Apply’ to import the FEM.

Note

Optionally, review the "Include Files" for this FEM.

01_FEMImport.png

Setup Design Loads

  1. Proceed to the FEA Results Tab.

  2. Open the ‘Design Loads’ form.

    01_FEMImport_Results.png

  3. Set LFLim = 1/1.4 = 0.714 for all cases (use ctrl+a to select all).

  4. Click ‘Apply’ to save.

    02_DesignLoads.png

Part 2: Organize Model into HyperX Entities

Create Structures

  1. Use the FEM tree to isolate desired panels using the Include File.

    panelsInFEMTree

  2. Select panels

  3. Right click > Create Structure

  4. Select ‘Create Structures per Include File’

  5. Select ‘Assign Designs’

    createStructuresFromInclude

Map Missing FEM Material to HyperX Material

“HyperX found a material in your FEM that isn’t mapped to one in your Database. Would you like to create a new material with the FEM card definition or map it to an existing?”

linkMaterial

Review the Structure Tree to see there is a Structure created per each INCLUDE file in the FEM

Review the Panel Designs in the Property Tree

Note

Each assigned Design Property corresponds to a property card in the FEM and all are set to Analysis mode.

image9.png

Setup Composites for Analysis

Let's clean up the model a bit to get a clear view of what we're looking for. Select all of the Structures we just created, right-click, and select "Show Only".

showOnlyIncludeStructures.png

Use the Property Tree to hide all metal plates.

image10.png

  1. Apply existing Peak Load Property to all panels.

  2. Apply ‘Sandwich and Ply NASA CCM’ Analysis Property to all panels.

image11.png

Note

These properties came from the Database Template – to illustrate a workflow in which all company/program policies are specified in the Database to remove ambiguity between engineers

Analyze Composite Panels and Review Margins

Select all composite panels (the entire visible model at this point) and click Analyze (not Size). We've assigned a Filtered Load Property with Peak Element load processing yielding results on a per-Zone basis.

initialAnalysisResults

Using the Legend and Analysis Watch Window, we can see that the upper shell contains negative composite strength margins. Let's run an element-by-element margin assessment to better understand the problem.

Setup Upper Shell for Element-based Assessment

  1. Select the negative upper shell panel > Right-Click > Show Only.

  2. Assign the existing Element-Based Load Property to the panel.

assignElementBased

Run Element-Based Assessment and Review Margins

Re-Analyze the selection. Then, select the “By Element” option in the Legend window to show element-based margins.

elementBasedResults

Show Analysis Results Window

Right-click on the Zone and select "Analysis Results" to open the Analysis Watch Window. Notice negative element-based margin is the same as the peak element margin (as to be expected).

elementBasedAWW

Part 3: Size Upper Skin and Interrogate Results

Show Critical Design Case

Show critical load case plot with the Legend to see which case is controlling the negative elements. Design Case 922 and 923 are critical for the panel at the location of the negative margin elements.

controllingDesignCase

Plot Deformations for Critical Case

Using the "Deform" tab of the Legend, we can plot deformations for critical load cases. For better context, switch back to plotting MS on the Legend and show the rest of the vehicle. Then, on the Deform tab:

  1. Set the dropdown to "Deformed".

  2. Set the "Factor" to 50. This controls how much the deformation is exaggerated in the Viewport. Higher values will make it more visible.

  3. Select the 922 or 923 Design Load Case.

  4. Notice negative elements are being pulled by the overlaying fitting.

deformCriticalCase

Plot Critical Failure Mode

Back on the "Plot" tab of the Legend, we can overlay the critical Failure Mode (Controlling Criterion) on the deformation plot. The elements of interest are failing in composite strength.

plotCriticalFailureMode

Use Data Probe

Let's use the Data Probe to get a descriptive screenshot of the problem area and corresponding data.

  1. Show only the Zone we were looking at earlier.

  2. Open the Data Probe from the Result tab of the Ribbon.

  3. Select "Auto Label" and click on one of the negative MS elements to add a Label to it.

  4. Change the Legend plot and select ‘Add Data’ to add the corresponding results to the Probe Label. We can add the MS, Controlling Case, and Controlling Criterion.

probeLabel

Plot Element Nxy Loads for Critical Case

The negative elements have high negative shear loads.

plotNxyForCritCase

Show Panel Cross-sections

Notice the design is ‘stepping’ with each composite panel section. This is likely the cause of the high shear loads in the panel.

image21.png

Show Panel Reference Plane

  • Select the panel > Right Click > Panel Settings.

  • View reference plane of the panel of interest to better understand the load path.

  • In this case, the reference plane is at the bottom of the panel.

image22.png

Revisit the Analysis Watch Window

Re-opening the Analysis Watch Window shows that it is the BOTTOM face that is driving the negative strength margin. This makes sense, as the previous step showed that this is where the load is applied.

image23.png

Review Design for Negative Panel

  • Show margin plot for the entire upper shell, for context

  • Select Panel > Right-Click > Design Property

  • Panel is currently 4-core-4, per FEM definition

image24.png

Part 4: Make Adjustments and Resize

Show Design for Adjacent Panel

Because we know the adjacent panel is thicker (think back to the cross-section plot), we can use that to our advantage. Repeat previous step to see the adjacent panel design.

The adjacent panel is 6-core-6. Extending this 6-ply-facesheet design into the negative elements will likely mitigate the negative strength margin in the bottom face.

image25.png

Add Negative Elements to Adjacent Panel Zone

  • Show only the panel in question and the adjacent panel.

  • Find the appropriate Zone in the Structures Tree by:

    1. Select the adjacent panel in the Viewport.

    2. Use the ‘Viewport Sync’ button on the Structure tree.

image26.png

  1. Right-Click on the adjacent panel Zone.

  2. Select ‘Edit’ to edit the element membership in that panel.

image27.png

  • Use the Legend bins to add only the negative elements.

    1. Hold Shift + Click the Red and Orange Color bins (corresponding to the negative margins).

    2. Select ‘Apply’ in the editing window.

image28.png

Re-analyze Panels and Review Results

Negative margins have been mitigated by adding an additional two plies to each facesheet in afflicted elements.

image29.png

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